In telecommunication networks, particularly in the telephone loop network, connection between the loop and the drop or service line to a customer's premises is commonly effected at a terminal block located in an aerial, or with the more recent practice of utilizing underground cable, a pedestal terminal. The terminal block which has long been employed in this role comprises simply one or more pairs of threaded metal posts embedded in an insulating body of dielectric material and carrying spacing metal washers and a tightening nut. Each one of a pair of such posts is permanently affixed to a respective tip and ring wire comprising a wire pair of the local loop cable, and connection of a customer service line pair is accomplished by wrapping each of those service wires about its appropriate post between the washers and tightening down the nut.
While the enclosure of the terminal structure, a pedestal for example, shields the terminal block and its connections from vandalism and the intrusion of larger animals, it provides little practical protection from smaller animals and insects, or from the greater danger of moisture and environmental exposure. Telephone line performance can thus suffer from the occasional shorting resulting from the bridging of terminal posts by resident animals, the webs of spiders, and the like. More regularly, however, the bridging is brought about, and the terminations themselves damaged, by corrosion of the exposed metal parts of the terminal block.
Such corrosion is induced and promoted by the constant moisture of the environment, whether it be from condensation, precipitation, or flood, coupled with the continuous electrical potential that is maintained between the tip and ring wires of a working pair, and consequently between the corresponding terminal block posts. As corrosion of these parts continues, the corrosion products accumulate and spread over the surface of the block body until the space between posts is physically bridged to form a high resistance short across the circuit.
Previous attempts at preventing this damaging corrosion have included the reshaping of the terminal block body to form extended pedestals to support the terminal posts, thus increasing the block surface distance between posts. This approach served to prolong the interval until bridging occurred, but did little to deter the inevitable corrosion. Protective caps or boots filled with waterproof dielectric grease or gel and fitted individually over each terminal post subsequently showed some promise as a protective, corrosion-inhibiting means; however, the temporary, removable nature of these devices significantly reduced their continuing value. The failure of these and other attempts, prior to the present invention, to eliminate the corrosion at terminal block posts had left the industry constantly subject to the extensive losses and expenditures resulting from this phenomenon.